Countdown for Argentina's longest TBM drive Jul 2012
Peter Kenyon, TunnelTalk
Final testing is under way in preparation for Argentina's longest ever TBM drive to replace underground a 35km section of the busy Sarmiento rail line in the western suburbs of Buenos Aires. As part of the project 15 stations along the alignment will also be relocated underground. Contractor for the major urban redevelopment is the Sarmiento New Consortium (SNC), which comprises IECSA (Argentina); Odebrecht (Brazil); Ghella (Italy) and COMSA (Spain) and an 11.26m diameter Herrenknecht EPBM has been procured to complete single-tube double-track tunnel.
  • Fig 1. Tunnel will be constructed in  three phases

    Fig 1. Tunnel will be constructed in three phases

  • Herrenknecht 11.26m diameter TBM cutterhead

    Herrenknecht 11.26m diameter TBM cutterhead

The estimated BRL11 billion (US$5.8 billion) project, awarded originally to SNC in 2008, is to be built in three phases:
• Phase 1 - Haedo to Caballito for a total length of 16.67km with eight new underground stations;
• Phase 2 – Haedo to Castelar for a total of 3.95km, including two new underground stations, and;
• Phase 3 – Castelar to Moreno for 14.09km with a further five relocated stations underground.
The Herrenknecht TBM is being assembled at the base of the central Haido working shaft for a start of tunnelling on Phase 1 scheduled in September (2012). The 16.67km drive to Caballito is expected to breakthrough in 2015.
  • Table 1. Herrenknecht 11.26m TBM specifications
    Maximum operating pressure 4 bar
    Cutting capacity 6,300 kW
    Cutter head rotation speed 3.1 rpm
    Total thrust 120,753 kN
    Torque rating 44,082 kNm
    Separation torque 54,221 kNm
    Gross weight 2,100 tonne
    Overall length 125m
    Minimum curve radius 220m
    Segmental lining ring 6 segment + key
    Length of rings 1800mm
    Tunnel i.d. 10.46m
    Excavation o.d. 11.26m
  • Fig 2. Sarmiento gold line to run underground to Moreno

    Fig 2. Sarmiento gold line to run underground to Moreno

The design is for the 10.46m i.d. single-tube double-track tunnel to accommodate double-deck metro trains. While fit-out, track laying and systems installations is underway on Phase 1, the TBM will excavate the tunnel drives for Phases 2 and 3, which are scheduled to take another 50 months to complete. The at-grade Sarmiento commuter line carries 10 million rail passengers each month from the western suburbs into Buenos Aires city centre and will remain open throughout the construction.
The primary reason for relocating one of the busiest commuter lines in Buenos Aires underground is safety. There are 81 level crossings on the at-grade Sarmiento line, 52 for traffic and 29 for pedestrians. In September 2011, 19 people died when a bus went through an open barrier crossing and was hit a train approaching the Flores Station platform. The devastating crash was caught on film by station platform CCTV cameras. In February (2012), 51 people were killed in a train crash at the Once Station on the line.
"This is the most important railway project [in Argentina] of the last 100 years," said Transport Minister Florencio Randazzo. "The elimination of the level crossings will help avoid many accidents and much loss of life."

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